Device for reversing the direction of drive of an inked ribbon in a high-speed printer

ABSTRACT

A device for reversing the direction of drive of an inked ribbon in a high-speed printer has a crank arm which guides the inked ribbon such that when the ribbon nears the end of its length and must be reversed a pull is exerted on the crank arm which pivots the crank arm. A feed pawl on the crank arm pivots a ratchet wheel through a small angle and cam wheels rotating with the ratchet wheel actuate a cam lever which in turn engages the actuator of a microswitch connected in circuit with a synchronous motor which is reversible by the switch.

United States Patent [1 1 Pfiz 1 1 DEVICE FOR REVERSING THE DIRECTION OF DRIVE OF AN INKED RIBBON IN A HIGH-SPEED PRINTER [75] Inventor: Albert Pfiz,Niedcrst0tzinge n,

Germany [73] Assignee: Walther Buromaschinen GmbI-I,

Gerstetten, Germany [22] Filed: Oct. 5, 1973 [21] Appl. No.: 403,780

[30] .Foreign Application Priority Data Oct. 6, 1972 Germany 224911 1 [52] US. Cl. 101/336; 197/162 [51] Int. Cl B41j 33/516 [58] Field of Search ..197/l51,160,161,162,

[56] References Cited UNITED STATES PATENTS Schenk 197/162 X [451 May 13, 1975 Primary ExaminerClifford D. Crowder Attorney, Agent, or Firm-Edmund M. Jaskiewicz [57] ABSTRACT A device for reversing the direction of drive of an inked ribbon in a high-speed printer has a crank arm which guides the inked ribbonsuch that when the rib-,

bon nears the end of its length and must be reversed a pull is exerted on the crank arm which pivots the crank arm. A feed pawl on the crank arm pivots a ratchet wheel through a small angle and cam wheels rotating with the ratchet wheel actuate a cam lever which in turn engages the actuator of a microswitch connected in circuit with a synchronous motor which is reversible by the switch.

3 Claims, 5 Drawing Figures DEVICE FOR REVERSING TI-IE DIRECTION OF DRIVE OF AN INKED RIBBON IN A HIGH-SPEED PRINTER The present invention relates to driving the inked ribbon in a high-speed printer, more particularly, to a device for automatically reversing the direction of the drive of the ribbon.

Various forms of devices have been proposed for reversing the direction of drive of an inked ribbon after the ribbon has been unwound from one spool so that the operative length of the ribbon has been exposed to the printer. The direction of movement of the ribbon is then reversed by electrical flip-flop circuits including amplifiers and sensing levers. The precise moment of reversal is usually sensed by means of microswitches. The use of these relatively high priced electronic components significantly increases the number of parts of the printer and thus substantially increases the cost of the printer. A further disadvantage is that the sensing levers generally employed in such devices are rather unreliable in actual practice since, whenever the inked ribbon must be replaced, the levers must be pivoted out of and then back into the range of the spool. This pivoting and movement of the levers frequently causes operating errors with respect to the reversal of the ribbon.

It has also been proposed to incorporate in such reversing devices light beams passing through openings in the ribbon which means energize photoelectric cells which then produce the necessary pulse signal required to initiate the direction reversing operation. Another form of ribbon reversing arrangement comprises an electrically conducting portion on each end of the ribbon. The ribbon is permanently in contact with a fixed electrical contact or switch and after the ribbon has been unwound the electrically conducting portion will close a circuit on the contact device so that one motor may be switched off and the other motor switched on by means of a relay so as to change the direction of movement of the ribbon. However, these devices 'and arrangements have been generally unsatisfactory in practice since they are relatively expensive with respect to the components required, complex in structure and thus bring about increased costs of manufacture and assembly. In addition, the inked ribbons must be modified or specially prepared and in this connection reference is made to the German publication document OS 1 436 658.

It is therefore the principal object of the present invention to provide a novel and improved device for reversing the direction of drive of an inked ribbon in a high-speed printer for data processing machines and the like.

It is another object of the present invention to provide such a ribbon reversing device which is simple in construction, embodies a minimum of components and is relatively inexpensive to manufacture.

It is a further object of the present invention to provide such a ribbon reversing device wherein a conventional inked ribbon can be employed and which will be reliable and precise in operation over long periods of time.

According to one aspect of the present invention a device for reversing the direction of drive of an inked ribbon in a high-speed printer may comprise a pivotally mounted crank having a guide pin on one of its lever arms such that a ribbon is guided over the pin. A feed pawl is pivotally mounted on the other of the crank lever arms andis continuously urged by a spring into engagement with a rotably mounted ratchet wheel. A pair of cam wheels are interconnected with the ratchet wheel so as to be rotatable therewith. A cam lever is operatively engagable with the cam wheels and has an arm which is engagable with an actuator of a microswitch. A synchronous motor drives the ribbon and is electrically connected to the microswitch so as to be reversible thereby. The microswitch is actuated by the cam lever in response to the cam wheels upon angular movement of the ratchet wheel by the feed pawl when the crank arm is pivoted in response to a pull by the ribbon on the guide pin immediately prior to rewinding of the ribbon at which point the ribbon has been unwound from one spool.

Other objects and advantages of the present invention will be apparent upon reference to the accompanying description when taken in conjunction with the following drawings, which are exemplary, wherein;

FIG. 1 is a plan view of the ribbon reversing device in its normal position according to the present invention;

FIG. 2 is a side view of the device of FIG. I viewed in the direction of the arrow A;

FIG. 3 is a plan view of the ratchet wheel and cam wheel components of the device of FIG. 1 showing the parts in position subsequently to switching of the direction of drive of the ribbon;

FIG. 4 is a view similar to that of FIG. 3 and showing the components back in the normal position; and

FIG. 5 is a block diagram showing schematically the electrical circuit for reversing the direction of rotation of the synchronous motor driving the ribbon.

Proceeding next to the drawings wherein like reference symbols indicate the same parts throughout the various views a specific embodiment of the present invention will be described in detail.

With particular reference to FIGS. 1 and 2 there is illustrated an inked ribbon 1 which is driven continuously by a synchronous motor in a high-speed printer in a manner which is known in the art and is accordingly not shown in the drawings. The ribbon 1 is actually reciprocated between two winding spools so as to be moved past a printing position or line of the printer in a manner known in the art. The ribbon is positioned over and guided upon a pin 5 which extends outwardly from an arm 2 of an angular or crank lever 4 pivotally mounted on shaft 3. When the ribbon 1 is in one of its end positions at which position it is unwound from one spool and completely wound on the other spool the additional drive on the ribbon will produce an increased tension or pull upon the ribbon. Since the ribbon is guided upon the pin 5 this additional pull will produce a force represented by the arrow 6 which acts on the guide pin 5 of the arm 2 in a counterclockwise direction. The crank lever 4 is provided with a second arm 7 which is urged against the pull of force 6 by means of a tension spring 8. However, the pull of force 6 tends to pivot the arm 7 in the direction of the arrow 9.

A feed pawl 11 is pivotally mounted on the outer end 7 of the arm 7. A spring 10 acts upon an end of the feed pawl 11 so as to urge the feed pawl continuously into engagement with teeth 12 of a ratchet wheel 12 rotatably mounted on a shaft 13. The ratchet wheel pivots through an angle defined by the space between the teeth 12' in the direction indicated by the arrow 14.

Cam wheels and 16 are secured to the ratchet wheel 12 so that the cam wheels will move through the same pivot angle as the ratchet wheel and simultaneously therewith. A cam lever 18 is pivotally mounted on a pin 17 and on one end thereof has a sensing projection or feeler portion 19 which rides on the outer periphery 15' of the cam wheel 15 until such a time that the feeler portion 19 drops into a recess 15". This will occur at the end of the pivoting path of the cam as shown in FIG. 3. The cam lever 18 has a second arm 21 which is subjected to the action of tension spring 20 in such a manner that the arm 21 acts upon a plunger or actuator 22 of a microswitch 23.

A synchronous motor 24 is connected electrically with the microswitch 23 in the manner shown schematically in FIG. 5. The motor 24 is thus reversible in response to actuation of microswitch 23 and its reversal of direction of rotation reverses the direction of feed of the inked ribbon.

After the inked ribbon 1 has been rewound, the resulting force which is again produced by the pull of the ribbon and represented by the arrow 6 as described above in FIG. 1 again causes a switching movement or pivoting of the cam wheels 15 and 16 through a predetermined pivot angle by means of the drive provided by the feed pawl 11 acting upon the ratchet wheel 12 as described above. As shown in FIGS. 3 and 4, the feeler portion 19 of the cam lever 18 which is presently situated in a recess 15" will now be cammed upwardly on a sloping surface 15" up to the outer peripheral surface 15' of cam wheel 15 so that the cam lever 18 is again pivoted into its normal position against the action of tension spring 20 as seen in FIG. 1. During the return pivoting of cam lever 11, a cam 16' on the cam wheel 16 will maintain the plunger 22 of microswitch 23 in the depressed position of FIG. 3 until the cam lever 18 is pivoted back to its original position. Upon return of the cam lever 18 to its normal position the actuator 22 will then abrubtly spring back into its position as shown in FlG. 1 which will effect a reversal of the synchronous motor 24 and accordingly a reversal of the direction of feed of the inked ribbon l.

The above described sequence of operations is repeated after every rewinding of the inked ribbon during the switching operation of the ratchet wheel 12 together with the cam wheels 15 and 16.

It is therefore apparent that the present invention has disclosed a simple but effective device for reversing the direction of drive of an inked ribbon in a high-speed printer. Only a slight increase in the tension upon the ribbon when it has been unwound from a spool is necessary to pivot the crank arm 19 and cause its feed pawl to switch or pivot the ratchet wheel 12 and cam wheels 15 and 16 through the small angles necessary to affect the switching step.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions, and accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

What is claimed is:

1. A device for reversing the direction of drive of an inked ribbon in a high-speed printer for data processing machines and the like comprising a pivotally mounted crank arm having first and second lever arms, a guide pin extending laterally from said first lever arm and adapted to guide an inked ribbon thereon, a feed pawl pivotally mounted on said second lever arm, a rotatably mounted ratchet wheel and interconnected first and second cam wheels rotatable therewith, spring means continuously urging said feed pawl into engagement with said ratchet wheel, a cam lever operatively engagable by said cam wheels, a microswitch engagable by said cam lever to be actuated thereby, and a synchronous motor drivingly connected to said inked ribbon and electrically connected to said microswitch so as to be reversible thereby, said microswitch actuated by said cam lever in response to said cam wheels upon angular movement of said ratchet wheel by said feed pawl when said crank arm is pivoted in response to a pull by the ribbon on the guide pin prior to rewinding of the ribbon.

2. A device as claimed in claim 1 wherein said first cam wheel has peripheral recesses thereon, said cam lever having a feeler portion cooperating with said recesses and an arm engagable with an actuator of said microswitch to actuate said switch.

3. A device as claimed in claim 2 wherein said second cam wheel has cams thereon engagable with the actuator arm of said microswitch to maintain said actuator arm in the actuated position while said cam lever is being cammed into its normal position by a recess on said first cam wheel. 

1. A device for reversing the direction of drive of an inked ribbon in a high-speed printer for data processing machines and the like comprising a pivotally mounted crank arm having first and second lever arms, a guide pin extending laterally from said first lever arm and adapted to guide an inked ribbon thereon, a feed pawl pivotally mounted on said second lever arm, a rotatably mounted ratchet wheel and interconnected first and second cam wheels rotatable therewith, spring means continuously urging said feed pawl into engagement with said ratchet wheel, a cam lever operatively engagable by said cam wheels, a microswitch engagable by said cam lever to be actuated thereby, and a synchronous motor drivingly connected to said inked ribbon and electrically connected to said microswitch so as to be reversible thereby, said microswitch actuated by said cam lever in response to said cam wheels upon angular movement of said ratchet wheel by said feed pawl when said crank arm is pivoted in response to a pull by the ribbon on the guide pin prior to rewinding of the ribbon.
 2. A device as claimed in claim 1 wherein said first cam wheel has peripheral recesses thereon, said cam lever having a feeler portion cooperating with said recesses and an arm engagable with an actuator of said microswitch to actuate said switch.
 3. A device as claimed in claim 2 wherein said second cam wheel has cams thereon engagable with the actuator arm of said microswitch to maintain said actuator arm in the actuated position while said cam lever is being cammed into its normal position by a recess on said first cam wheel. 